// ========================================================================
// Copyright 2006 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ========================================================================
package org.mortbay.cometd.continuation;
import javax.servlet.http.HttpServletResponse;
import org.mortbay.cometd.ClientImpl;
import org.mortbay.log.Log;
import org.mortbay.thread.Timeout;
import org.mortbay.util.ajax.Continuation;
/* ------------------------------------------------------------ */
/**
* Extension of {@link ClientImpl} that uses {@link Continuation}s to resume
* clients waiting for messages. Continuation clients are used for remote
* clients and have removed if they are not accessed within an idle timeout (@link
* {@link ContinuationBayeux#_clientTimer}).
*
* @author gregw
*
*/
public class ContinuationClient extends ClientImpl
{
private final ContinuationBayeux _bayeux;
private final Timeout.Task _intervalTimeoutTask;
private final Timeout.Task _lazyTimeoutTask;
private long _accessed;
private volatile Continuation _continuation;
private volatile boolean _lazyResuming;
/* ------------------------------------------------------------ */
protected ContinuationClient(ContinuationBayeux bayeux)
{
super(bayeux);
_bayeux=bayeux;
if (isLocal())
{
_intervalTimeoutTask=null;
_lazyTimeoutTask=null;
}
else
{
// The timeout task for when a long poll does not arrive.
_intervalTimeoutTask=new Timeout.Task()
{
@Override
public void expired()
{
remove(true);
}
@Override
public String toString()
{
return "T-" + ContinuationClient.this.toString();
}
};
// The timeout task for lazy messages
_lazyTimeoutTask=new Timeout.Task()
{
@Override
public void expired()
{
_lazyResuming=false;
if (hasMessages())
resume();
}
@Override
public String toString()
{
return "L-" + ContinuationClient.this.toString();
}
};
_bayeux.startTimeout(_intervalTimeoutTask,_bayeux.getMaxInterval());
}
}
/* ------------------------------------------------------------ */
public void setContinuation(Continuation continuation)
{
synchronized (this)
{
Continuation oldContinuation = _continuation;
_continuation = continuation;
Log.debug("Old continuation {}, new continuation {}", oldContinuation, continuation);
// There can be a suspended old continuation if the remote client reloads or
// somehow re-issues a new long poll request with an outstanding long poll request.
// In this case we resume() the existing continuation, otherwise
// it will expire, this method is entered again with a null argument, and a timeout
// to expire this client will be scheduled (which is wrong because client expiration
// must be handled by the new continuation and not by the old one, which dies here)
if (oldContinuation != null && oldContinuation.isPending())
{
try
{
int responseCode = HttpServletResponse.SC_REQUEST_TIMEOUT;
Log.debug("Sending {} on old continuation {}", responseCode, oldContinuation);
HttpServletResponse response = (HttpServletResponse)oldContinuation.getObject();
response.sendError(responseCode);
}
catch(Exception x)
{
Log.ignore(x);
}
try
{
Log.debug("Resuming old continuation {}", oldContinuation);
// The response is committed so this resume() will be blocked by ContinuationCometdServlet
oldContinuation.resume();
}
catch (Exception x)
{
Log.ignore(x);
}
}
if (continuation == null)
{
// Set timeout when to expect the next long poll
if (_intervalTimeoutTask != null)
_bayeux.startTimeout(_intervalTimeoutTask, _bayeux.getMaxInterval());
}
else
{
_bayeux.cancelTimeout(_intervalTimeoutTask);
_accessed = _bayeux.getNow();
}
}
}
/* ------------------------------------------------------------ */
public Continuation getContinuation()
{
return _continuation;
}
/* ------------------------------------------------------------ */
@Override
public void lazyResume()
{
int max=_bayeux.getMaxLazyLatency();
if (max>0 && _lazyTimeoutTask!=null && !_lazyResuming)
{
_lazyResuming=true;
// use modulo so all lazy clients do not wakeup at once
_bayeux.startTimeout(_lazyTimeoutTask,_accessed%max);
}
}
/* ------------------------------------------------------------ */
@Override
public void resume()
{
synchronized(this)
{
if (_continuation != null)
{
_continuation.resume();
}
_continuation=null;
}
}
/* ------------------------------------------------------------ */
@Override
public boolean isLocal()
{
return false;
}
/* ------------------------------------------------------------ */
public void access()
{
synchronized(this)
{
_accessed=_bayeux.getNow();
if (_intervalTimeoutTask != null && _intervalTimeoutTask.isScheduled())
{
// reschedule the timer even though it may be cancelled next...
// it might not be.
_intervalTimeoutTask.reschedule();
}
}
}
/* ------------------------------------------------------------ */
public synchronized long lastAccessed()
{
return _accessed;
}
/* ------------------------------------------------------------ */
/*
* (non-Javadoc)
*
* @see org.mortbay.cometd.ClientImpl#remove(boolean)
*/
@Override
public void remove(boolean wasTimeout)
{
synchronized(this)
{
if (!wasTimeout && _intervalTimeoutTask != null)
_bayeux.cancelTimeout(_intervalTimeoutTask);
}
super.remove(wasTimeout);
}
}